[Base] All: Add Base Mainnet and testnet as a network on Grants Stack

[michellema1208]

User Story:
As a Grants Stack user
I want to be able to use Grants Stack on Base
So that I can run a round on Base

Acceptance Criteria
GIVEN that I am on Grants Stack (Builder / Manager / Explorer)
WHEN I click on the network selection toggle
THEN I see that Base is a supported network

GIVEN that I am on Manager
WHEN I am setting up a round on Base
THEN I see payout token options are USDC or ETH

GIVEN that I am on Explorer
WHEN I am donating to projects in a round on Base
THEN I can set my donations on Base to be in USDC or ETH

Product & Design Links:
N/A

Tech Details:
From Allo team:
Allo v1 contracts: https://github.com/allo-protocol/allo-contracts/blob/main/docs/CHAINS.md
Graph PR: allo-protocol/deprecated-graph#33
Graph: https://api.studio.thegraph.com/query/45391/grants-round-base/v0.0.1
Deploy PR: allo-protocol/allo-contracts#104

• Chain Deploy Checklist: https://www.notion.so/gitcoin/Chain-Deploy-Checklist-d4ed8c6664f14ac3b2da0f0d9c9a6219
• Allo graph deployments: https://github.com/allo-protocol/graph/tree/main/round

Open Questions:

Notes/Assumptions:

• This includes writing test coverage for the functionality added in the ticket, if necessary